The present invention relates generally to bicycles and, more particularly, to a bicycle wheel assembly that is constructed to directly engage a portion of a bicycle frame.
Known bicycle wheel assemblies generally include a hub that is centrally positioned relative to a rim that is shaped to receive a tire. One such wheel assembly 10 is shown in FIG. 5. As shown in FIG. 5, a number of spokes 11 extend between a hub 12 and a rim to maintain the generally concentric orientation of hub 12 and the rim. Hub 12 includes a hollow cavity 16 that is constructed to receive an axle 18 and a bearing element 20 at generally opposite sides thereof. Although axle 18 could be solid, many axles are hollow and constructed to receive a skewer rod 24 that passes through the axle 18 and engages a portion 26 of a bicycle frame 30, such as a fork, such that the alternate portions 26 generally flank the wheel assembly. In a front wheel application, portion 26 of frame 30 is commonly referred to as a fork, and axle 18 and skewer rod 24 are constructed to cooperate with a dropout 32 formed near the end of each respective fork. An end cap 36 is disposed between each bearing 20 and the respective dropout 32. A head 40 is engaged with the opposite ends of skewer rod 24 and secures wheel assembly 10 to frame 30. Although wheel assembly 10 provides a generally robust wheel assembly, it is not without its respective drawbacks.
The interaction of the drop outs 32 with the ends of axle 18 requires the inward spacing of the opposite bearings 20 and end caps 36 relative to the respective drop out 32. Each end cap 36 cooperates with hub 12 and axle 18 so as to provide the desired spacing associated with the distance between the forks 30. Axle 18, skewer rod 24, bearing 20, and hub 12 must be constructed to accommodate the offsetting of each bearing 20 inboard relative to the distal ends of axle 18 and the interface with dropout 32. The robust structure of these components increases the mass associated with wheel assembly 10.
Furthermore, the numerous individual interfaces between the various components of wheel assembly 10 further complicate both wheel assembly and manufacture. Axle 18 must be constructed to cooperate with a bearing 20 and end cap 36 positioned at the alternate ends of the axle as well as the pair of dropouts 32. Hub 12 must also be provided with an interior geometry configured to cooperate with each bearing 20 and end cap 36. Assembly and wheel maintenance requires that each bearing 20 and end cap 36 be associated in their appropriate position relative to hollow axle 18 and hub 12.
In addition to the assembly complications described above, wheel assembly 10 is also susceptible to decreased lateral stiffness do the interaction of the multiple components positioned at the interface between hub 12 and the pair of dropouts 32. The interaction of each bearing 20 and end cap 36 pair relative to axle 18 and hub 12, as well as the inboard offsetting of each bearing 20 with respect to the adjacent dropout 32, introduces some degree of lateral deflection of wheel assembly 10 during operation of a bicycle so equipped. Although wheel assembly 10 may be acceptable for some rider's expectations, such deflection may be unacceptable for other riders.
Therefore, there is a need for a bicycle wheel assembly that is lightweight and robust and that exhibits desired lateral stiffness and longevity for both the wheel and the wheel hub assembly.